Among surfactants for synthetic detergents, a linear alkylbenzenesulfonate (hereinafter sometimes abbreviated to LAS), which is an anionic surfactant, has been sold and used since 1967 instead of a branched alkylbenzenesulfonate (ABS), which has poor biodegradability, according to the recommendation of the administrative. Since LAS is cheap and its toxicity is low, it is still using as a main component of household synthetic detergents. However, recently, water pollution by LAS and its degradation products have been a social problem because of the discharge of drainage from living into rivers, etc. Then, the tap water standard of anionic surfactants has been established (not more than 0.2 mg/liter). In addition, nonionic surfactants are used as about 40% of surfactant compounds for synthetic detergents and establishment of its tap water standard is being studied.
Under these circumstances, synthetic detergents and their degradation products in an environment are determined and analyzed and the results are utilized for environmental preservation. As methods for such determination and analysis, for example, high-performance liquid chromatography (HPLC) and gas chromatography (GC) are employed for quantitative determination of detergents and their degradation products in tap water, rivers, swamps, lakes or sewege etc. However, the problems of these methods are such that they require expensive apparatus or devices, pretreatment and the operation with great skill. As official methods for measuring anionic surfactants and nonionic surfactants, there are methylene blue absorption method and potassium zinc (II) tetrathiocyanate method, respectively. However, these methods require, for example, extraction with organic solvents which are harmful to human beings and complicated concentration steps and therefore, improvement of these methods is expected.
In view of these problems, regarding anionic and nonionic surfactants, it is desired to develop a method for determination thereof which can maintain present high sensitivity and can be readily and quickly operated with high specificity at a low cost.
As one means for solving these problems, an enzyme-linked immunosorbent assay (hereinafter sometimes abbreviated to ELISA) can be considered.
Assay systems and kits utilizing ELISA have been constructed for various other environmental pollutants. For example, WO 94/12536 discloses ELISA for detecting petroleum fuel in an environment and a kit for such ELISA. The kit comprises an enzyme and an antibody, and the measurement can be completed very quickly, usually, within several hours. And, the operation is very simple in comparison with conventional HPLC and GC, and, in most cases, no complicated pretreatment required in such conventional methods is needed. Further, a very specific determination can be carried out by using an antibody, in particular, a monoclonal antibody. HPLC and GC require very expensive apparatus and devices and their maintenance is also expensive, while ELISA has no such problem.
However, any immunoassay method which can be used for detection and determination of synthetic detergents including LAS, in particular, ELISA has not yet been established.